(1) Field of the Invention
The present invention relates to a device for shaping laser radiation which has sub-beams spaced apart in a first direction perpendicular to the propagation direction of the laser radiation, in particular for shaping laser to radiation which is output by a laser diode bar.
Definitions: in the propagation direction of the light to be influenced means the average propagation of the light, particularly when it is not a plane wave or is at least partially convergent or divergent. Light beam, sub-beam or beam, unless expressly indicated otherwise, does not mean an idealized ray of geometrical optics but a real light beam, for example a light beam with a Gaussian profile, which has an extended rather than infinitesimally small beam cross section.
Laser diode bars have a multiplicity of emitters, for example 19 emitters, which are arranged spaced apart in the so-called slow axis. The slow axis is the aforementioned first direction in which the active layer of the semiconductor diode extends, while the fast axis is the direction perpendicular thereto. For example, each of the emitters has a length of about 150 μm in the slow axis, the distance between two neighboring emitters in this direction being about 400 μm. The effect of this is that there are dark regions between the sub-beams output by the individual emitters, which are found to be disadvantageous for the brightness (specific intensity) of the laser radiation.
(2) Description of Related Art
In the prior art the sub-beams of laser diode bars, which are output by the individual emitters, are collimated by micro-optics in the fast axis and sometimes also in the slow axis, without the periodicity of the beams of the individual emitters being manipulated. An example of this may be found in WO 2005/085934 A1. In this prior art, further beam-shaping optics are therefore used in order to achieve a particular beam profile, depending on the application. The dark region between the emitters is tolerated, which places a limit on the achievable brightness. Owing to the bar structure, there is therefore a design-related limit for the brightness of the overall laser system which is markedly different from the physical limit.
Another example of beam-shaping optics may be found in DE 101 06 155 A1. There, the laser radiation output by a laser diode bar is split into two parts in the slow axis, these parts subsequently being superimposed on one another in the fast axis. The cross section of the laser radiation is therefore converted from an elongated rectangular shape into a less elongated rectangular shape, which can be focused better onto the end of a light guide fiber.